The other day I was pooping and reflecting over Jaina's recent behavior, and I came to this conclusion: Azshara is controlling her and probably Aethas too.
Think about it, the next expansion is practically confirmed to be The Dark Below (IF it is, damn, people are so dumb and cant keep on one thought), and I bet that Azshara will be a major character, In the War of the Ancients, Azshara is described to be hilariously powerful and preferring to use mind control and charm spells upon her subjects, so I think that she saw an opportunity to take Jaina's mind when she was unstable by the Mana Nuke, It would make perfect sense since she can manipulate behind courtains and all aggression would be seen as "justified", you know shes angry and all, she wants to undermine the Horde and the Alliance, she told Varian to dismantle the Horde, if Varian had done so, the Alliance would be crippled and the Horde would cease to exist, to the benefit of Azshara and her old god master. About Aethas, maybe he is being mind controlled too, he has always been mysterious and cryptic.
I wouldnt be surprised if 6.1 had a raid boss called The Mage Puppets or something where we have to fight Jaina and/or Aethas in order to free them from Azshara's control.
EDIT: Because people cant really read.